This time I would like to point out, what I think is, a bug in the "Dynamic Backlight" dimming function on every 32" PFL9705 and at least some (if not all) 40" and 46" PFL9705, the 58" PFL9955, plus the latest 58" PFL9956, 40" and 52" PFL9606 and even the 46" PFL9706. This bug can be very annoying, especially in darker scenes.

In this short sample I made of the movie "Entrapment" (never mind the fuzziness, it was big enough already), you can clearly see the dimming of the upper part of the picture every time subtitles appear at the bottom.

Why!?... It may be to increase contrast even further (unnecessary, as it is strong enough), but I would rather leave parts of the picture where nothing is changing alone. Because when you don't, the dimming (every time subtitles appear) and undimming (every time they disappear again) is very apparent, as nothing should be changing in those parts at all.

Please Philips, it would be great if you could improve the Local Dimming function at this point, as I think it is the last big disadvantage of an otherwise great feature!

I've tested your video sample on my 32PFL9705H/12 (fw 0.140.32.0) and I've got the same problem, just as you described.
I've tried also to change the video settings (normal, live, energy saving, etc.) and the problem remain.
I think is the same behavior that the tv has when it shows information messages (eg. when you select the option to disable the "light sensor", the tv shows a pop-up box that is brighter than the rest of the image)

Yes indeed, that doesn't matter, as long as "Dynamic Backlight" is activated (Standard/Optimal).

Originally Posted by Adamo

I think is the same behavior that the tv has when it shows information messages (eg. when you select the option to disable the "light sensor", the tv shows a pop-up box that is brighter than the rest of the image)

Yes, that can trigger it too when the picture is dim enough. Turning the sound on or off is another example.

I just wanted to let you... Philips... know that this problem is still present in the latest firmware 140.34.
So... I really hope you will be working on this as much as you are on the persistent sound problem.

For me this is now the only problem that's really bothering me. The sound problem doesn't happen very often in my case, but this dimming problem happens more than I originally thought...
You see, a lot of the scenes where this problem occurs are the same as where previously the dark backlight bands were shown, so... now that those are gone, this has become a lot more apparent.

I'm really looking forward to a solution, as that would make the picture close to perfect for me!...

Dynamic backlighting: The name already explains what it does; Normally the backlight brightness is fixed. In some Philips TVís you can choose to make it dynamic. At dark scenes or pictures there will be more brightness of the backlight and at bright scenes there will be less brightness. The backlight brightness is based on the average light output.

It is a great feature when you watch a picture slideshow or movies without subtitles.

It is annoying when watching a movie with subtitles. The subtitles are in bright white; they make a big change in the average screen brightness, so the TV is responding to that for the whole screen.

If you donít like it, turn it off! So, it is not a bug and it canít be fixed in these TVís.

In the ďhigh-end rangeĒ this is not an issue. There the backlight is a comlete matix of LEDís behind the LCD screen. Every bright spot in the picture is lighted-out locally. So brightness of subtitles do not affect brightness elsewhere on the screen.

Dynamic backlighting: The name already explains what it does; Normally the backlight brightness is fixed. In some Philips TVís you can choose to make it dynamic. At dark scenes or pictures there will be more brightness of the backlight and at bright scenes there will be less brightness. The backlight brightness is based on the average light output.

It is a great feature when you watch a picture slideshow or movies without subtitles.

Hmmm... what'll I do!?... Simply ignore this "wise" lesson, or...

Originally Posted by DellUser

It is annoying when watching a movie with subtitles. The subtitles are in bright white; they make a big change in the average screen brightness, so the TV is responding to that for the whole screen.

If you donít like it, turn it off! So, it is not a bug and it canít be fixed in these TVís.

In the ďhigh-end rangeĒ this is not an issue. There the backlight is a comlete matix of LEDís behind the LCD screen. Every bright spot in the picture is lighted-out locally. So brightness of subtitles do not affect brightness elsewhere on the screen.

It would not have have been a bad idea to have a look at what kind of TV we're talking about here... as our 32PFL9705 is definitely "high-end range" with "a complete matrix of LEDís behind the LCD screen"!

That's really interesting, as so far I've only had reports from 32PFL9705 owners here.
So just to be sure, when watching the "Entrapment" fragment I posted, you also notice the dimming of the upper part of the picture when subtitles appear, and the subsequent brightening of the picture when the subtitles disappear again?...

That's really interesting, as so far I've only had reports from 32PFL9705 owners here.
So just to be sure, when watching the "Entrapment" fragment I posted, you also notice the dimming of the upper part of the picture when subtitles appear, and the subsequent brightening of the picture when the subtitles disappear again?...

When i watch the SubtitleDimming.mpg I can see the problem that you also notice. I can see a change in the area around the subtitles. I also, not alle the time, notice a change in the rest of the image when subtitles comes on. This is the same problem that I have when I watch blurays. On my TV this change can happen both when subtitles are on and off, but more often when subtitles are on.

So now it seems this unwanted effect is not specific to the 32" PFL9705, but also happens on the 40" and 46" versions.

May I make a few suggestions to improve this, Philips?... (As if you would need my suggestions... )

It looks like this bad effect occurs, because the intensity of neighboring LED zones is adapted to the intensity of the zone(s) where something is happening (subtitles appearing in this case). I can understand why you are doing this (to lessen the halo effect around bright objects), but I think this should be done in a very, very limited way. After all, the function is called LOCAL Dimming.

The way it is now, it can happen that the appearance of a bright object in the upper left corner, effects the LED intensity in the lower right corner as well!... That can't be right, can it!?...

So my suggestions are:

1. - make the dimming effect more local than it is now. Direct neighbors may influence each other slightly, but not any further zones.
It seems that now the intensity of a LED zone is effected not only by the brightness of the picture in that zone, but also on the INTENSITY (instead of the picture brightness) of the neighboring LED zones.
This can be seen by looking at a dim picture and then putting something bright on screen (by turning on/off the sound for example). When you do this, you can see the dimming effect spread over the screen: the first zones to react are where the action is (upper left in this case), but then more and more zones react to that (towards the middle and finally even in the lower right).
To overcome this unwanted effect, no longer take into account the neighboring zones' LED intensity anymore. Only take into account the picture brightness in the zone itself as well as in its direct neighbors.

This would make it perfect and, for me, this would be my favorite solution.
Another possibility could be:

2. - make a new setting, in which the user can set the level of locality: 0 would mean not local at all (i.e. as if it were a global dimming system), whereas 10 would be completely local (i.e. neighboring zones are not taken into account at all).

That way the user could make its own choice between the different advantages and disadvantages of local dimming, depending on the source material.
And finally my least favorite option:

3. - if nothing else works, an exception could be made for subtitles, causing them not to influence the rest of the picture.

I hope some of these ideas are helpful to you!... I'm really looking forward to your solution!
Thanks again in advance!

Just put it on USB and watch it on your PFL9705, making sure "Dynamic Backlight" is activated.
Now that it's on your screen, turn the volume (yes, the sound ) on or off, up or down.

The symbol that appears in the upper left corner then does the "trick".
Of course you see the picture become slightly brighter there where the symbol appears. That's because the LED's in the upper left corner zone become more intense, as they should.

But now look at the lower left corner... Notice the picture actually dims there as soon as the volume symbol appears on screen?... This happens because the LED's in the lower left corner zone become LESS intense, and that should definitely not happen!

This is the same problem as the one I started this thread with, it's just a little easier to test it this way.

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